Methods and Instrumentation for Synchrotron Radiation Research

Sub-natural Linewidth RIXS

At the present state-of-the-art beamline at SLS, we have recently demonstrated that vibrationally resolved RIXS is feasible in gases and liquids as well as complex materials. This gives unique information about processes on the femtosecond time scale, and implies a new tool for investigation of local details of the electronic ground state in large molecular systems.

RIXS with ultimate sub-natural linewidth resolution offers the opportunity to resolve individual molecular vibrational states and gives a new tool to study the fundamentals of the coupling between the electronic and nuclear degrees of freedom on the femtosecond time scale. RIXS back to the ground state creates a vibrational progression (Fig. 1), thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems.

In combination with accurate theoretical modeling this can be extended to investigations of strongly interacting liquids with large variations in the local potential, strongly correlated solids and superconductors and fundamental aspects of gas-phase dynamics.

We are building, commissioning and operating a new RIXS end station with sub-natural linewidth resolution at BESSYII. We are planning to perform time-resolved RIXS with sub-natural linewidth resolution at the free-electron laser facility XFEL in Hamburg (Germany) and plan for the ultimate high-resolution RIXS facility at BESSYII.